Concrete · Columns & walls

RC column (N–M interaction) calculator

Short rectangular column, uniaxial bending: interaction diagram, minimum moment and slenderness.

Standard: AS 3600-2018 Cl 10.3, 10.6

Inputs in the worked example

The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.

Diagram for the worked example

Rectangular stress block α2 = 0.790, γ = 0.850, εcu = 0.003, Es = 200 GPa
Nuo = α1 f'c (Ag − As) + fsy As, α1 = 1 − 0.003f'c (0.72…0.85)
Curve by strain compatibility, varying neutral-axis depth
φ = 0.65 above Nub; below, φ = 0.65 + (φ0 − 0.65)(1 − Nu/Nub), φ0 = 1.24 − 13ku/12
Minimum M* = N*·0.05D (Cl 10.1.2)
r = 0.3D; braced short if Le/r ≤ max(25, αc(38 − f'c/15)(1 + M1/M2)); unbraced ≤ 22

RC cantilever retaining wall stem — Factored earth and surcharge moment at the stem base, vertical reinforcement and shear capacity (pair with…
Column biaxial bending (AS 3600) — Load-contour check (Mx*/φMux)^αn + (My*/φMuy)^αn ≤ 1 for a rectangular column, with the exponent αn derived…
Slender RC column (moment magnifier) — Slenderness, buckling load Nc, moment magnifier δb and the magnified design moment checked against the N–M…
RC wall: in-plane shear and simplified axial capacity — Braced reinforced concrete wall resisting in-plane horizontal shear and vertical load. Shear capacity Vu =…
Circular RC column: N–M interaction — Circular column or pile section with bars evenly spaced round a circle. The interaction curve is built by…
Basement wall propped top and bottom — Basement wall spanning vertically between the floor slab at the top and the basement slab at the bottom…
RC wall: simplified axial capacity — Braced wall design axial strength per unit length with eccentricity and the slenderness eccentricity ea =…

For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.